watchface and currentHeartRate which models?

I think the chronos does, but the thing is it doesn't support onPartialUpdate() so you can't see it changing all the time.  Same with the vahr.

The f5x and variants (like the Descent) don't, and it's due to a difference to support maps on those devices.

The Approach S60 is similar to the f5x in this way.

The f5 plus devices support it as well as the va3 and 645 devices.

What I do is if Activity.getActivityInfo().currentHeartRate is null, is I just use the newest reading from getHeratRateHistory(), so on devices where currentHeartRate is always null, the HR still changes every minute or two.

Thank you jim_m_58

Regarding Chronos I thought the same.

Vahr and Approach S60 are not CIQ 3.0 (are not selectable as build target with minimum 3.0 SDK).

I've found in one or two other threads where you posted that D2 Charlie and Fenix 5 also don't support it.
Can you confirm again?

About coding: your suggestion is what I already do in UltraSlim watch face.
I just needed a list of devices that don't support it, because some users complain about it. :-D

While they aren't CIQ3, the access to Activity.Info.currentHeartRate is the same.  On some it will change, some it will always be null.

And null is normal for any device if you aren't wearing it.

That's why I just do the null check, and if null, check the newest reading in getHeartRateHisory if so. (which may also indicate a null/invalid reading.)

Hi mates!

So it seems the Fenix Chronos is now on CIQ 3.1.x, but does not support OnPartialUpdate?

is it possible or did I do a mistake somewhere in my code?

if I put 

PUA = ( Toybox.WatchUi.WatchFace has :onPartialUpdate );

it returns false (true for other devices.

The first devices with the HW to support onPartialUpdate was the f5 series and 935.

The Chronos predated that and doesn't have the HW.  No 1hz on the chronos.